The present invention relates to solid pharmaceutical compositions and the method of preparing the same. More specifically, the present invention relates to the preparation of stabilized pharmaceutical compositions, using pharmaceutically active ingredients such as levothyroxine sodium and liothyronine sodium (thyroid hormone drugs), in a solid dosage form. Said stabilized hormone compositions are prepared by blending the active moiety and β-sheet form of microcrystalline cellulose and compressing to the desired solid dosage forms.
Thyroid hormone preparations of levothyroxine sodium and liothyronine sodium are pharmaceutical preparations useful in the treatment of hypothyroidism and thyroid hormone replacement therapy in mammals, for example, humans and dogs.
Thyroid hormone preparations are used to treat reduced or absent thyroid function of any etiology, including human or animal ailments such as myxedema, cretinism and obesity.
Hypothyroidism is a common condition. It has been reported in the United States Federal Register that Hypothyroidism has a prevalence of 0.5 percent to 1.3 percent in adults. In people over 60, the prevalence of primary hypothyroidism increases to 2.7 percent in men and 7.1 percent in women. Because congenital hypothyroidism may result in irreversible mental retardation, which can be avoided with early diagnosis and treatment, newborn screening for this disorder is mandatory in North America, Europe, and Japan.
Thyroid hormone replacement therapy can be a chronic, lifetime endeavor. The dosage is established for each patient individually. Generally, the initial dose is small. The amount is increased gradually until clinical evaluation and laboratory tests indicate that an optimal response has been achieved. The dose required to maintain this response is then continued. The age and general physical condition of the patient and the severity and duration of the hypothyroid symptoms determine the initial dosage and the rate at which the dosage may be increased to the eventual maintenance level. It has been reported that the dosage increase should be very gradual in patients with myxedema or cardiovascular disease to prevent precipitation of angina, myocardial infarction, or stroke.
It is important that thyroid hormone treatment have the correct dosage. Both under treatment and over treatment can have deleterious health impacts. In the case of under treatment, a sub-optimal response and hypothyroidism could result, under treatment has also been reported to be a potential factor in decreased cardiac contractility and increased risk of coronary artery disease. Conversely, over treatment may result in toxic manifestations of hyperthyroidism such as cardiac pain, palpitations, or cardiac arrhythmias. In patients with coronary heart disease, even a small increase in the dose of levothyroxine sodium may be hazardous in a particular.
Hyperthyroidism is a known risk factor for osteoporosis. Several studies suggest that subclinical hyperthyroidism in premenopausal women receiving thyroid hormone drugs for replacement or suppressive therapy is associated with bone loss. To minimize the risk of osteoporosis it is preferable that the dose be kept to the lowest effective dose.
Because the risks associated with over treatment or under treatment with levothyroxine sodium, there is a need for thyroid hormone products that are consistent in potency and bioavailability. Such consistency is best accomplished by manufacturing techniques that maintain consistent amounts of the active moiety during tablet manufacture.
Thyroid hormone drugs are natural or synthetic preparations containing tetraiodothyronine (T4, levothyroxine) sodium or triiodothyronine (T3, liothyronine) sodium or both. T4 and T3 are produced in the human thyroid gland by the iodination and coupling of the amino acid tyroisine. T4 contains four iodine atoms and is formed by the coupling of two molecules of diiodotyrosine (DIT). T3 contains three atoms of iodine and is formed by the coupling of one molecule of DIT with one molecule of moniodotyrosine (MIT). Both hormones are stored in the thyroid colloid as thyroglobulin. Thyroid hormone preparations belong to two categories: (1) natural hormonal preparations derived from animal thyroid, and (2) synthetic preparations. Natural preparations include desiccated thyroid and thyroglobulin.
Desiccated thyroid is derived from domesticated animals that are used for food by man (either beef or hog thyroid), and thyroglobulin is derived from thyroid glands of the hog. The United States Pharamcopoeia (USP) has standardized the total iodine content of natural preparations. Thyroid USP contains not less than (NLT) 0.17 percent and not more than (NMT) 0.23 percent iodine, and thyroglobulin contains not less than (NLT) 0.7 percent of organically bound iodine. Iodine content is only an indirect indicator of true hormonal biologic activity.
Synthetic forms for both T4 and T3 thyroid hormone are available from a number of producers. For example, liothyronine sodium (T3) tablets are available from Jones Pharma, St. Louis, Mo. under the trademark Cytomel (now King Pharmaceuticals, Inc.) Levothyroxine sodium (T4) is available under the tradename Levoxyl from Jones Pharma (now King Pharmaceuticals, Inc.), under the tradename Synthroid from Knoll Pharmaceutical, Mt. Olive, N.J., and under the tradename Unithroid from Jerome Stevens Pharmaceuticals, Bohemia, N.Y. In addition a veterinarian preparation of levothyroxine sodium is available under the tradename Soloxine from Jones Pharma, St. Louis, Mo.
It is well known that the stability of thyroid hormone drugs are quire poor. They are hygroscopic and they degrade in the presence of moisture or light, and under conditions of high temperature. The instability is especially notable in the presence of pharmaceutical excipients, such as carbohydrates, including lactose, sucrose, dextrose and starch, as well as certain dyes.
It is desirable, therefore, to prepare a stabilized dosage of levothyroxine and liothyronine, which will have a longer shelf life that can be used in the treatment of human or animal thyroid hormone deficiency, U.S. Pat. No. 5,225,204 (the '204 patent) is directed to improving the stability of levothyroxine sodium. In one embodiment disclosed by '204, stabilized levothyroxine sodium was prepared in a dry state by mixing levothyroxine sodium with a cellulose tableting agent using geometric dilution and subsequently combining this mixture with the same or a second cellulose tableting agent, such as microcrystalline cellulose. Other tableting aids or excipients can be used in this formulation. This '204 patent is incorporated by reference herein in its entirety.
The microcrystalline cellulose disclosed in '204 is AVICEL 101, 102, 103, 105, trademarks of FMC Company of Newark, Del., and Microcrystalline Cellulose NF, or EMCOCEL, a trademark owned by Penwest Pharmaceuticals of Patterson, N.Y. These microcrystalline cellulose products are prepared by re-slurryng the cellulose and spray-draying the product. This produces an α-helix spherical microcrystalline cellulose product.
U.S. Pat. Nos. 5,955,015 and 6,056,975 (the continuation of '105) disclose a stabilized pharmaceutical preparation of levothyroxine and microcrystalline cellulose, along with other excipients. The microcrystalline cellulose products used by '105 and '975 were also the α-form Avicel microcrystalline cellulose products. U.S. Pat. Nos. 5,955,105 and 6,056,975 are incorporated by reference herein, in their entirety.
The microcrystalline cellulose product of the present invention is prepared by making a wet cake and drying it with a drum dryer, then passing the dried product through a screen or mill for sizing, which produces a β-sheet form microcrystalline cellulose which has a flat needle shape. Such β-sheet microcrystalline cellulose is marketed under the trademark CEOLUS KG801 by FMC Company of Newark, Del. Said Ceolus product has different morphology, and therefore different performance characteristics, than those of the Avicel product, and is suitable for preparing the present stabilized pharmaceutical product.
The β-sheet microcrystalline cellulose of the present invention is disclosed in the U.S. Pat. No. 5,574,150, which is hereby incorporated by reference. Further disclosure relating to β-sheet microcrystalline cellulose is found in International Journal of Pharmaceutics 182 (199) 155 which is hereby incorporated by reference.
The Ceolus product (β-sheet microcrystalline cellulose) is disclosed by FMC in its product bulletin dated October 1997 as being suitable for “smaller size tablets” and “exceptional drug carrying capacity.” Such Ceolus product was to provide superior compressibility and drug loading capacity that still exhibited effective flowability. The examples given in the bulleting are of vitamin C combined with Ceolus microcrystalline cellulose at levels of from 30 to 45 weight % Ceolus product in the form of a tablet. At higher levels of Ceolus product concentration, flow problems were encountered in the process of compressing tablets, and the Ceolus product was deemed unsuitable for compressions at higher concentrations than about 45 weight %.
None of the references listed above disclose the present invention of a stabilized pharmaceutical composition comprising a pharmaceutically active ingredient, such as levothyroxine, and at least about 50 weight % the β-sheet form of microcrystalline cellulose.